1. Field of the Invention
The present invention relates to a technology for managing a semiconductor manufacturing device.
2. Description of the Related Art
Better results can be obtained in a semiconductor manufacturing process if target parameters of a process are maintained at respective predetermined target values. For example, in a process of laminating a film, it is necessary to laminate a film with a desired width previously designed in the production recipe. Furthermore, in an exposure process, it is necessary that the dimensions after the exposure process are within an allowable range of the design values.
However, in semiconductor manufacturing processes, one or more target parameters may deviate from the target values due to various external causes. For example, in the exposure process, light exposure may change depending on a state of a lighting optical system or a state of a reticle that transfers a circuit pattern. Such a change of light exposure can cause dimensional change of a semiconductor. If the target parameters vary, elements that make up a semiconductor integrated circuit (IC) do not work in a desirable manner. Such a semiconductor IC is considered as a defective product and cannot be sold in the marketplace, resulting in decreasing a production yield.
One approach is to monitor a target parameter, i.e., a quality control (QC) value, for each process. Such monitoring includes monitoring a physical quantity, i.e., a QC value, while a process is being executed. Examples of QC values include resist width in the exposure process and finished dimensions of an element manufactured through a processing process.
It is common to monitor an internal state, so-called an equipment engineering system (EES) data, of the semiconductor manufacturing device by using various sensors. For example, in an exposure device used in the exposure process, several hundreds of EES parameters, such as light exposure, focus value, and temperature of a developer, are acquired.
JP-A 2005-197323 (KOKAI), discloses a conventional technology for identifying a cause of a variation of a QC value in a semiconductor manufacturing device from EES parameters by performing a correlation analysis on the QC value and the EES parameters.
Recently, an advanced process control (APC) has been developed. In the APC, a state of a manufacturing device is controlled based on a value of the target parameter to maintain a target parameter to a predetermined value. For example, in the exposure process, light exposure of the exposure device is controlled so that a resist width is maintained to a predetermined value based on the values of the resist width measured as the QC values. A linear relation can be seen between the light exposure and the resist width. Therefore, if it is detected a tendency from the QC values that the resist width become excessively wide, light exposure is controlled so that the resist width reduces to a desired value.
A fault detection and classification (FDC) is performed based on the EES parameters. FDC is a method of monitoring a parameter, such as an EES parameter, to check occurrence of a defect, and classify the defect when a defect has occurred. In the FDC, it is determined that a known defect has occurred when certain EES parameters have values in a predetermined range. In other words, in the FDC, it is necessary to prepare an FDC model for detecting defects based on EES parameters.
Maintenance operations are often performed on the semiconductor manufacturing device to maintain the device in a normal state. The maintenance operation includes, for example, cleaning of a vacuum chamber, or adjustment of various units. Although the semiconductor manufacturing device is maintained in a normal state by such maintenance operation, some of the EES parameters may vary unexpectedly due to the maintenance operation.
In the technique of identifying a cause of the change in QC values by using EES parameters, if the state of the device changes because an APC control or a maintenance operation is performed during an analysis period, the true cause of the change can not be extracted. Moreover, if the state of the device changes because an APC control or a maintenance operation is performed, the FDC model needs to be updated to suit the current state of the device. In other words, if one FDC model is used before and after an APC control or a maintenance operation, there is a possibility that a defect is erroneously detected or even overlooked.